Device for the treatment of a medical fluid

ABSTRACT

The invention relates to a device for the treatment of a medical fluid, said device consisting of a permanently installed fluid treatment machine and a cassette with fluid-carrying channels as well as an elastic matt placed between these two items, with matt channels recessed in said elastic matt. The matt channels are provided with slits. Via the matt channels, an optimised vacuum distribution takes place and the slits serve the purpose of removing air between the cassette and the fluid treatment machine.

[0001] The invention relates to a device for the treatment of a medicalfluid according to the preamble of claim 1.

[0002] Such devices are generally known and consist of a permanentlyinstalled fluid treatment machine, a cassette with fluid carryingchannels which are sealed with a foil, and an elastic matt placedbetween these two items. Medical fluids to be treated can be blood, forexample, but also dialysis fluids for the peritoneal as well as thehaemodialysis. The relevant cassettes are advantageously formed asdisposable units. Such a fluid treatment machine can also be a devicefor measuring of parameters of medical fluids, for example, as describedin the DE 198 37 667 A1.

[0003] In these devices, a low pressure is created between the elasticmatt and the cassette in order to prevent a deformation of the foilduring low pressure in the channel, which leads to a channel restrictionin the cassette, in order to be able to lift the foil at the addingpoints for the medical fluid and thus keep the access free, in order toprevent an air compliance in the pumping device and in order to be ableto guarantee at special sensor positions an air-free attachment betweenthe sensor surface and the foil.

[0004] The extraction of air requires openings on the machine and anextraction unit connected to them, a vacuum pump for example, wherebythe distribution of the vacuum should be guaranteed to be as evenly aspossible and positive across the entire foil surface of the cassette.

[0005] It is the object of the present invention to further develop thegeneric device such that, during operation, a problem-free airextraction is made possible whereby in this case the vacuum should beevenly distributed across the surface of the elastic matt and a simpleand problem-free air extraction should be possible while, during themachine's idle time, the openings necessary for the air extractionshould at least be largely closed.

[0006] In terms of the invention, this object is solved by thecombination of characteristics of claim 1. According to those, mattchannels are recessed in the elastic matt, with the path of saidchannels following the fluid-carrying channels of the cassette. Startingfrom a vacuum connection of the elastic matt to the extraction unit, thematt channels reach all important points of the elastic matt. In orderto avoid leaks when applying pressure to the channel beads of thetop-mounted cassette, these matt channels lie within the channelstructure of the cassette. Only where, within the cassette, too, thereis a channel or another fluid-carrying structure as part of thecassette, there is also a corresponding matt channel in the elasticmatt. In the matt channels, slits have been placed. These slits providedin the elastic matt behave in a similar manner as a lip seal. As aresult of applying a vacuum, air can be extracted from between the fluidtreatment machine and the cassette because the perimeter areas of theslits are pulled in due to the vacuum and its connection to an opening.However, due to the return force of the elastic material, these slitsclose immediately once the vacuum connection is interrupted, i.e. whenthe device is in an idle state or when there is no significantdifferential pressure. In this state, an ingress of fluid is securelyprevented. On the other hand, when the slits are open, the access to theextraction unit, i.e. the continuation from the matt to the vacuum pump,can be protected against unintended ingress of fluid by suitablemeasures (e.g. filter).

[0007] Preferred embodiments of the invention can be seen from thedependent claims following the main claim.

[0008] Thus, along the matt channels, the slits can be interruptedrepeatedly for short intervals. That way, the slits are afforded asufficient stability which enhances their valve function.

[0009] At certain points, a continuation of the vacuum line is notpossible via the matt channels that run within the cassette channelsbecause there are, for example, recesses provided in the elastic matt,which interrupt the matt channels. These recesses engage, for example,with pump membranes or valves on the machine. This structure would leadto a situation where a trouble-free air extraction via the matt channelscan no longer take place. In order to nevertheless provide a fullsurface contact between the cassette and the machine, with said contactbeing as leak-proof as possible, and in order to extend the requiredvacuum source efficiently to the various areas of the contact surface,additional flatter connection channels compared to the matt channels areformed here, which by-pass the large-area recesses within the elasticmatt. The execution of these connection channels is so shallow and sonarrow that the nearby matt material of the elastic matt retainssufficient self-stability in order to prevent a deformation and closingof the connection channel even during the application of the vacuum andthe distortion. Due to this preferred design, it is guaranteed that theslits and channels during distortion and application of the vacuumremain open and the matt remains sufficiently stable while the sealingeffect of the matt remains intact and the channel structure provided issufficient for the air flow to be extracted.

[0010] Finally, in the preferred arrangement, the elastic matt isdesigned to be exchangeable.

[0011] Further details and advantages of the invention are explainedmore closely by way of an embodiment shown in the drawing. Shown are:

[0012]FIG. 1: a schematic, 3D representation of a section of an elasticmatt according to an embodiment of the present invention,

[0013]FIG. 2: a section along the section line A-A′,

[0014]FIG. 3: a section along the section line B-B′, and

[0015]FIG. 4: a section along the section line C-C′.

[0016] In FIG. 1, an elastic matt 10 is shown schematically which isarranged between a fluid treatment machine, of which no detail is shownhere, and a cassette (disposable) which is usually formed as adisposable unit. On the so-called machine side, namely on the surfacewhich, when assembled, faces the fluid treatment machine, matt channels12 and connection channels 14 are formed. Furthermore, a recess 16 isarranged in the elastic matt 10, into which in the assembled condition amachine-mounted valve, for example, engages and establishes a seal allaround. It is easy to see that this machine-mounted valve interrupts therespective matt channel 12 which happens to join the recess 16. In orderto still make an air extraction possible, a connection channel 14 hasbeen provided which connects the two interrupted branches of mattchannel 12 and connects them in turn with a further, parallel mattchannel 12. The structure shown here is, of course, only an example andcan be changed in any way. While the channel structures are provided onthe machine side of the elastic matt 10, the disposable side, namely theside facing the cassette, is executed as a smooth, i.e. flat surface.

[0017] By referring to the sectional views of FIGS. 2 to 4, thestructure of the individual channels can be explained in more detail.The section A-A′ as per FIG. 1 is shown in FIG. 2 where a matt channelbecomes visible which, with the elastic matt used here having athickness of 4 mm, has a depth of 3 mm and a width of 2 mm. In theremaining matt material below channel 12, which has a thickness of 1 mm,a slit 18 is placed which takes on a type of valve function. When avacuum is applied, the two areas of the elastic matt 10 adjacent to theslit 18 will open and enable the extraction of air gas. In an idle stateor when an equilibrium is obtained, the two adjacent areas return totheir original position and close the opening. In order to enhance thisreturn effect, areas between the slits 18 are provided in the mattchannel 12, which on the one hand do not have a slit and, on the otherhand, are less deeply recessed in the area of matt channel 12. Acorresponding area can be seen in section B-B′ as per FIG. 3 which showsthat, while the matt channel 12 in this area has the same width of 2 mm,it only has a depth of 1 mm.

[0018] In the view as per FIG. 4, a connection channel 14 is shown inthe sectional view of C-C′, where said channel is narrower and not asdeep as the matt channel 12, which can be seen clearly in this view. Inthis case, both the width of the connection channel 14 and the depth areone millimetre each.

[0019] With the elastic matt according to this invention, it isguaranteed that the interior space of the fluid treatment machine, inits idle state, is protected by the self-closing feature of slits 18. Atthe same time, an even air extraction is achieved between the fluidtreatment machine and the cassette across its entire surface becauseparallel extraction takes place via numerous slits 18. Thus, a minorblockage may not cause any detrimental effects for other areas.

[0020] With a thin matt 10, as it has been presented in the embodimentfor example, the opening effect of the slits can be utilised by applyinga vacuum.

[0021] Since the elastic matt 10 is exchangeable, it can be replacedeasily after contamination or a fault. It is especially advantageousthat no structured shapes are required for the fixed components on themachine. On the side of the elastic matt 10 facing the machine, openstructures can be formed so that no sub-surface tunnels or other closedstructures are required. On the other hand, the side of the elastic matt10 facing the cassette is largely formed as a smooth, closed surfacewhich can be cleaned easily for example.

1. A device for the treatment of a medical fluid, said device consisting of a permanently installed fluid treatment machine, a cassette with fluid carrying channels and an elastic matt placed between the fluid treatment machine and the fluid-carrying channels, characterised in that matt channels are recessed in the elastic matt, with the path of said channels following the fluid-carrying channels of the cassette and that slits are provided in the matt channels, which extend from the matt channels to the side facing the cassette.
 2. The device according to claim 1, characterised in that the slits along the matt channels are repeatedly interrupted for short intervals.
 3. The device according to claim 2, characterised in that the matt channels in the slitted areas are more deeply recessed than in the non-slitted areas.
 4. The device according to claims 1 to 3, characterised in that the elastic matt has shallower connection channels compared to the matt channels, in particular for continuation around interruptions in the matt channels which are intended for the attachment of machine-mounted pump membranes and valves for example.
 5. The device according to claims 1 to 4, characterised in that the elastic matt is exchangeable.
 6. The device according to claims 1 to 5, characterised in that the elastic matt is sealable in the perimeter area of the cassette by putting pressure onto a circumferential seal edge contained within the cassette area.
 7. The device for the treatment of a medical fluid, said device consisting of a permanently installed fluid treatment machine and an elastic matt for attaching a cassette with fluid-carrying channels, characterised in that matt channels are recessed in the elastic matt with the path of said channels following the fluid-carrying channels of the attachable cassette and that slits are provided in the matt channels with said slits extending from the matt channels to the side facing the attachable cassette.
 8. An elastic matt for the use in a device according to one of the claims 1 to
 6. 